1. Field of the Invention
The present invention relates to an Asynchronous Transfer Mode (ATM) switching system, and more particularly to a system and method for controlling duplexing in an ATM system.
2. Background of the Related Art
In general, an ATM switching system uses an asynchronous transfer mode, in which user information is formed as a cell. The cell includes a five byte header sector including destination information for transmission the information, and a 48 byte payload sector including data information. The user information is transmitted through an output port using switching according to the information recorded in the header sector.
FIG. 1 is a schematic block diagram of a related art ATM switching system. As shown in FIG. 1, when an audio signal, a video signal, data, or the like, to be transmitted to a prescribed destination is inputted into an ATM multiplexer 1, the ATM multiplexer 1 forms a cell. The cell includes data information and destination information for the inputted signals. The ATM multiplexer transmits the cell to an ATM switch 2. Then, the ATM switch 2 switches an output port of a destination of transmission, based on the received header information of the cell, and outputs an output of the cell through the output port.
The ATM switching system, which transmits information by means of a cell as described above, includes two boards having the same construction. These boards are respectively maintained in an active state and in a standby state. Inter-processor communication (IPC) for exchanging information between processors is maintained between the processors of the two boards, so as to maintain stability and reliability in the transmission/reception of data.
In such an ATM switching system, when a first board in an active state is separated or the system experiences trouble, the first board executes a switching of duplexing procedure. By doing this, the first board transfers active authority and data information, which has already been processed by the first board to a second board, which is in a standby state. It does this through an IPC communication. When the trouble of the first board has been settled, the first board is maintained in the standby state.
FIG. 2 shows a schematic block diagram of a related art duplexing system, which can continuously operate an ATM switching system, even when a board is separated or the ATM switching system experiences trouble.
As shown in FIG. 2, each of boards A and B includes a high speed serial input/output (SIO) board A2 and B2 for rapidly transmitting/receiving information between the boards. Accordingly, when switching from Board A (the present board) to Board B (the opponent board) in order to transmit/receive state information between the boards having the duplexing construction and data processing information, data required in the SIO communication needs to be changed and restored (i.e. segmented and reassembled). This delays the receipt of information by the opponent board. It further results in a loss of the transmitted/received data in the course of processing it into data necessary in the SIO communication. Moreover, when the SIO board experiences trouble, the transmission/reception of information between the boards is not carried out, and normal switching of duplexing is thus not performed.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.